Pedicle hooks having bifurcated blades are described for example, in J. Dubousset and Y. Cotrel Orthopade (1989) 18:118-127, "Die CD-Instrumentation in der Behandlung von Wirbel-Saulendeformitaten" (CD Instruments in the treatment of spinal column deformities). Such devices have a symmetrical indentation in the blade and can be used indiscriminately for the left and the right pedicles of the vertebral column. The purpose of the indentation in such hooks is to prevent the hook from sliding when a load is placed on it from the side, which can cause injury to the dura. Accordingly, an anatomically correct indentation that is as deep as possible is sought. The indentation of the blade of such prior pedicle hooks is centrally positioned and is completely symmetrical. Its medial and lateral dimensions are therefore equal. The height of the two legs formed by the bifurcation is limited by the width of the pedicle hook and the shape of the indentation, which in turn are adapted to the anatomy in question. In such symmetrical designs, the disadvantage is the continuing danger that the pedicle hook will slip medially under pressure and thereby injure the spinal marrow.